For aircraft safety reasons, there is a need to detect attitude faults. One typical approach to detecting attitude faults is to have redundant attitude systems combined with some sort of comparison method. When the redundancy is down to only two attitude systems and they disagree, it can be difficult to decide which one is in error. In this case, and in other cases in general, a system that can detect attitude faults is needed. A system that is capable of detecting attitude faults is referred to as an attitude monitor.